The general purpose of the research is to elucidate the mechanisms of intestinal absorption and secretion, with emphasis on fluid secretion. It is proposed to extend our previous studies of the passive permeability of the dog small intestine, and of pressure induced intestinal secretion. Studies will be made of the details of the microcirculatory pattern of the intestinal villus. Attempts will be made to elucidate the mechanism of the acetylcholine evoked alkaline secretion of the dog stomach.